Compressor advice please

[dalgrae]

Can someone please advise me about a compressor choice I hope to make for my garage.I have 2 in mind

The first is a 14cfm belt drive twin producing approx 8.1 cfm free air from a 90ltr tank.

The second is a 14cfm direct drive v twin producing approx 9.5 cfm free air from a 50ltr tank.

I intend to use it to power a small 75 mm air polisher which is rated at 3.0 cfm ,I also intend to buy an air drill and a couple of other tools all rated at a max of 4 cfm.Both of my choces are on offer at the moment for the next few days VAT free so I need to take advantage of this saving ,both are single phase the v twin is local to me which I see as a good thing the belt drive would be by the internet /courier. I have been made aware as seems normal what ever compressor is bought that there is a maximum number of starts per hour in the above choices this is 12.Do I assume that the motor can run for a certain time it is the starts that cause the problem ,so once the motor kicks in it will run OK
So my question is please what would be the best choice

[irmscher]

Dalgrae try mig-welding .co.uk it tells you everything on there a brilliant site

[kevin s]

The belt drive will be quieter otherwise it is down to the quality of the machine and air volume. I have not heard about a limited numer of starts before mine dont seem to have this limitation. I would imagine it is due to the capacitor used to start the induction motor.

[bmcecosse]

The larger tank will mean fewer 'starts' - so probably best to go for that assuming similar price inc delivery. The comp cfm sounds quite high for what you propose to run - do you intend to do any spraying? That's what usually takes the highest air demand - and you don't want to have to stop part way through a panel while the pressure builds up again...

[philthehill]

As a minimum go for the next size up from the one that you think you need or even the largest size single phase you can get because if you start low you cannot add to its uses. I have a SIP Airmate 13/50-SRB 3Hp belt driven air compressor with a 50ltr tank and whilst the air delivery is adequate I should have bought one with a 100 ltr tank. I use mine for all sorts of tasks and would not be without it. One of the most useful bits of kit in my wksp.
Make sure that you get a moisture trap and if you do use an air drill use an in line oil lubricator to lubricate the vanes otherwise the air drill will not last long.
Drain the tank after every use or the tank will fill with water and the air capacity will be reduced even further.
I got mine in the sale at Halfords a few years back so now is the time to buy and grab yourself a bargain!!!
Merry Christmas

[bmcecosse]

It's very easy to add on an extra receiver....empty propane cylinder makes an excellent receiver - and is protected by the safety valve on the compressor. Only connect it in the system when you NEED the extra capacity (ie spraying/fitting tyres) otherwise it's a waste of power filling it - and then leaving it to leak away when finished with the air.

[dalgrae]

Thanks for all the advice, I will now have to make my mind up but have already decided on the fitment of a lubricator into the system as advised .If any spraying is required it will only be on a small scale on a panel by panel basis.

[philthehill]

GENERAL ADVICE - Whilst it is good to use an extra cylinder to make up compressed air capacity make sure that the air receiver is serviceable and if possible has a current air receiver test certificate. Having in the past been a certified examiner of air receivers I have seen some very poor condition air receivers that I would not want to put 20lb/sq in into let alone 100lb/sq in. It is important to note that the compressor blow off valve does not determine the pressure that a badly rusted air receiver needs to explode.
An air receiver exploding through corrosion is not a nice thing to be on the receiving end of.
I have always examined my air receivers internally/externally on a regular basis and if there is any sign of excessive corrosion it is scrapped.

[dalgrae]

Roy I have sent you a PM , regards Colin

[irmscher]

Dalgrae on that site I sent you it tells you what compressor etc and has a full section on what you need

[les]

I might be reading things wrong, so bear with me. My spray plant has the blow off valve on the air receiver. not on the compressor.

[kennatt]

I might be reading things wrong, so bear with me. My spray plant has the blow off valve on the air receiver. not on the compressor.

most do,but a rusted/damaged reciever.will still only blow off at the preset pressure when new,but the tank itself may explode way before that pressure is reached,think thats what phil is saying.

[philthehill]

Kennatt
Exactly right.
The tank could explode at any pressure and the higher the pressure the more damage it can cause.
To that end I would never recommend the purchase of a S/H compressor unless it comes with a current safety certificate for the compressor tank and safety/blow off valve or the purchaser is competent to examine the air receiver both inside and outside and the safety/blow off valve.
Only use air receivers designed for receiving compressed air it is not worth the risk in using non compliant cylinders.
All new compressors/air receivers even for the DIY market come with a test and compliance certificate.. Make sure that you have them when purchasing.
A serviceable and compliant air receiver should be able to withstand a test pressure of at least 1 & 1/2 times working pressure with out failing. Details should be plated on the tank.

[smithskids]

My compressor is only 3 cu.ft/min but I did what bmc has done ie added 3 ex brewery co2 cyls into the circuit after the line drain. If you have a lubricator fitted dont forget to bypass it when you are spraying.My co2 cylinders are mounted upside down and are self draining and easy to inspect for corrosion and pitting. To pressure test fill completly with water connect pressure gauge and gently heat up witha blowlamp to 1 1/2 times working pressure.easy.

[dalgrae]

Thanks again for all the replies.

I have decided on what compressor I will buy when they open tomorrow which will be a belt drive type ,the other interesting thing is this company also sells the 14cfm 3 hp v twin as advertised by several different companies at just under £200 as per the others but this includes free delivery ,also it comes with a 3 year warranty so they cannot be that bad on reliability as some of the forums state .